When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi guys,
I have 99 SC400 with 92k miles on it and my solenoid started to melt and drip the black butyl sealant. My rpms drop once the engine reaches the normal operating temperature and humming sound appears. I wonder if anyone has a spare solenoid that might consider to sell.
I have to drive with A/C on or car stalls at idle. Can't find it anywhere nationwide. Any help will be highly appreciated. Thank you
I have no idea, but it only happens once the engine is warm, I put on drive and rpms drop to 200-300 and weird humming sound appears (similar to power steering noise when is low on fluid). Turn A/C on and rpms jump to 600-700 range but the humming sound stays.
That switch is actually not for the hydraulic fan, it appears to be an Idle-Up Valve, which is there to increase the idle when the load on the pump goes up, Toyota had issues with it for the whole UZ engine run. First it was a vacuum diaphragm that, when the line pressure increased, opened, allowing more air into the engine. The problem with it was that it would start leaking after a while, throwing PS fluid into the intake.
Once the clutch fans were superseded, the PS pump was relocated to where the fan mount originally was, obtaining a new electrical switch in place of the vacuum one, here you can find detailed pictures of it. I wonder if the issue you are experiencing is the same leak problem as with the older style unit, are you sure it is glue seeping out of it and not the fluid?
To see if it really affects your idle, you can take the drive belt off and disconnect the switch, then go for a ride. Taking the belt off would eliminate the chance that one of the accessories is creating a drag, and disconnecting the wiring would prevent the switch from sending misleading data. If that will help, put the belt back on without connecting the switch, if the idle problems would return, the problem is with one of the accessories, so you will have to check each of them one-by-one. If the issue would only return when you reconnect the switch, just leave it disconnected until you can find a replacement, any later generation 1UZ-FE should have one.
What's the condition of your Power Steering Fluid? Judging from the pictures above, it is not a regular Vane Pump that most cars use, it is a Gear Pump, a lot like the one that is used in the engine block. They are not exactly efficient, but are cheap and very robust, so it can take a good while to kill one of those. If the Power Steering Pump will turn out being the cause of the whine, it is a very good reason to do an inspection of the whole steering system, including the rack.
I have the solenoid valve disconnected all the time now, no difference if its connected or not. It's dripping black butyl on the A/C compressor below it. I would like to start with replacing this part first before I move to something else, the only problem is that I can't find it anywhere. Already cleaned the throttle body, replaced spark plugs, pcv valve, checked the vacuum hoses, nothing helped. What I can't figure out is why the humming sound starts only once the engine is warm. Car runs and drives great, but I have to have a A/C on all the time.
Lexus calls the part VALVE, HYDRAULIC MOTOR CONTROL so is this a hydraulic valve that is controlling idle?
Huh, that's an explicit name.. Could it be called that way because it is activated by the pressure in PS system..? It is not exactly controlling the idle, per say, it just increases it when the load on the Power Steering is high to prevent the engine from stalling..
Originally Posted by lexensc400
I have the solenoid valve disconnected all the time now, no difference if its connected or not. It's dripping black butyl on the A/C compressor below it.
Have you tried taking the belt off when the cars starts stalling or the whine appears?
Originally Posted by lexensc400
I would like to start with replacing this part first before I move to something else, the only problem is that I can't find it anywhere.
Later models, as well as my 2000 ES300 got yet another version of that switch, relocating it in place of a banjo bolt for High Pressure line (P/N: 89438-33010 for the reference), I never had any issues with it. I wonder if it is possible to do a little retrofit, plugging the hole for an old switch and then replacing it with the newer style one? That could potentially solve a great deal of issues those switches caused in the past..
Originally Posted by lexensc400
Already cleaned the throttle body, replaced spark plugs, pcv valve, checked the vacuum hoses, nothing helped. What I can't figure out is why the humming sound starts only once the engine is warm. Car runs and drives great, but I have to have a A/C on all the time.
Have you tried checking Engine Live Data?
Is that humming sound in any way affected by the AC system?
How did the old spark plugs look, any unusual wear or gunk on them?
Check Fuel Trims, as well as MAF and A/F sensor readouts, among other parameters, if there is nothing unusual at the moment, see if there is anything out of place when the car starts stalling, which could yield interesting results.
Also, you wrote that the car can only stay alive if the AC is on, which seems more like an Idle Control Valve issue.. It is basically a stepper motor with a bimetallic spring as a fail-safe alternative, in case if the main motor would fail. Try disconnecting the IAC valve and turning the AC off, see if the stalling issue would return, the car won't be running silky-smooth, but it should stay running nonetheless..
05-21-22, 08:25 AM
Hydraulic Motor Valve 16929-50050
